You can connect multiple Radiobutton instances using a Tkinter variable so that when you click on a non-selected option, it will deselect whatever other option was previously selected.

In the following program, we created three radio buttons for the Red, Green, and Blue options. Each time you click on a radio button, it prints the lowercase name of the corresponding color:

import tkinter as tk

COLORS = [("Red", "red"), ("Green", "green"), ("Blue", "blue")]

class ChoiceApp(tk.Tk):
    def __init__(self):
        super().__init__()
        self.var = tk.StringVar()
        self.var.set("red")
        self.buttons = [self.create_radio(c) for c in COLORS]
        for button in self.buttons:
            button.pack(anchor=tk.W, padx=10, pady=5)

    def create_radio(self, option):
        text, value = option
        return tk.Radiobutton(self, text=text, value=value, 
                              command=self.print_option, 
                              variable=self.var)

    def print_option(self):
        print(self.var.get())

if __name__ == "__main__": 
    app = ChoiceApp()
    app.mainloop()

If you run this script, it will display the application with the Red radio button already selected: